Fairmount fund adds 150,000 Zenas BioPharma (ZBIO) shares

Rhea-AI Filing Summary

Fairmount Healthcare Fund II L.P., an entity associated with Fairmount Funds Management, reported an open-market purchase of 150,000 shares of Zenas BioPharma, Inc. common stock at $20.00 per share. After this transaction, the fund indirectly held 2,359,025 shares of Zenas BioPharma common stock.

Fairmount Funds Management LLC acts as investment manager to the fund, and its managers, Peter Harwin and Tomas Kiselak, along with Fairmount, disclaim beneficial ownership of the reported securities except to the extent of any pecuniary interest.

Insider Trade Summary

Net Buyer: 150,000 shares ($3,000,000)

Net Buy 1 txn

Insider Fairmount Funds Management LLC, Fairmount Healthcare Fund II L.P., Kiselak Tomas, Harwin Peter Evan

Role Director | Director | Director | Director

Bought 150,000 shs ($3.00M)

Type	Security	Shares	Price	Value
Purchase	Common Stock	150,000	$20.00	$3.00M

Holdings After Transaction: Common Stock — 2,359,025 shares (Indirect, By Fairmount Healthcare Fund II L.P.)

Footnotes (1)

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Key Figures

Shares purchased: 150,000 shares Purchase price: $20.00 per share Shares held after transaction: 2,359,025 shares +2 more

5 metrics

Shares purchased 150,000 shares Open-market purchase of common stock on March 31, 2026

Purchase price $20.00 per share Price paid for Zenas BioPharma common stock

Shares held after transaction 2,359,025 shares Indirect holdings by Fairmount Healthcare Fund II L.P. after purchase

Buy transactions 1 transaction Count of buy transactions in this Form 4

Net shares bought 150,000 shares Net buy volume reported in transaction summary

Key Terms

open-market purchase, indirect ownership, beneficial ownership, pecuniary interest

4 terms

open-market purchase financial

"transaction_action is described as an open-market purchase of common stock"

An open-market purchase is when an investor or a company buys shares on a public stock exchange at the going market price, rather than through a private deal. It matters to investors because these purchases change how many shares are available, can push the stock price up or signal confidence from large buyers, and often affect per-share metrics like earnings—think of it like someone buying lots of apples off a grocery shelf, reducing supply and potentially raising the price.

indirect ownership financial

"direct_or_indirect is coded as I, indicating indirect ownership by the fund"

beneficial ownership financial

"Fairmount and its managers disclaim beneficial ownership except for pecuniary interest"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

pecuniary interest financial

"they disclaim beneficial ownership except to the extent of their pecuniary interest"

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Fairmount Funds Management LLC

(Last) (First) (Middle)

200 BARR HARBOR DRIVE

SUITE 400

(Street)

WEST CONSHOHOCKEN PENNSYLVANIA 19428

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Zenas BioPharma, Inc. [ ZBIO ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/31/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	03/31/2026		P		150,000	A	$20	2,359,025	I	By Fairmount Healthcare Fund II L.P.(1)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person^*

Fairmount Funds Management LLC

(Last) (First) (Middle)

200 BARR HARBOR DRIVE

SUITE 400

(Street)

WEST CONSHOHOCKEN PENNSYLVANIA 19428

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Fairmount Healthcare Fund II L.P.

(Last) (First) (Middle)

200 BARR HARBOR DRIVE

SUITE 400

(Street)

WEST CONSHOHOCKEN PENNSYLVANIA 19428

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Kiselak Tomas

(Last) (First) (Middle)

200 BARR HARBOR DRIVE

SUITE 400

(Street)

WEST CONSHOHOCKEN PENNSYLVANIA 19428

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Harwin Peter Evan

(Last) (First) (Middle)

200 BARR HARBOR DRIVE

SUITE 400

(Street)

WEST CONSHOHOCKEN PENNSYLVANIA 19428

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. Fairmount Funds Management LLC ("Fairmount") is the investment manager for Fairmount Healthcare Fund II L.P. The managers of Fairmount are Peter Harwin and Tomas Kiselak. Fairmount, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein.

Remarks:

Fairmount may be deemed a director by deputization of Issuer by virtue of the fact that Tomas Kiselak serves on the board of directors of the Issuer and is also a Managing Member of Fairmount.

	/s/ Tomas Kiselak, Managing Member of Fairmount Funds Management LLC	04/01/2026
	/s/ Tomas Kiselak, Managing Member of Fairmount Healthcare Fund II, L.P.	04/01/2026
	/s/ Tomas Kiselak	04/01/2026
	/s/ Peter Harwin	04/01/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did Zenas BioPharma (ZBIO) report on this Form 4?

Fairmount Healthcare Fund II L.P. reported buying 150,000 Zenas BioPharma common shares at $20.00 each. The transaction was classified as an open-market purchase, indicating shares were acquired directly in the market rather than via option exercises or other derivative conversions.

Who is the actual buyer in the Zenas BioPharma (ZBIO) Form 4 filing?

The buyer is Fairmount Healthcare Fund II L.P., which holds the shares indirectly for reporting persons. Fairmount Funds Management LLC is the fund’s investment manager, and its managers are Peter Harwin and Tomas Kiselak, who report the transaction due to their roles.

How many Zenas BioPharma (ZBIO) shares does the Fairmount fund hold after the reported trade?

Following the transaction, Fairmount Healthcare Fund II L.P. indirectly held 2,359,025 Zenas BioPharma common shares. This total reflects the prior holdings plus the newly purchased 150,000 shares, all reported as indirect ownership through the investment fund structure.

What type of transaction is disclosed in this Zenas BioPharma (ZBIO) Form 4?

The filing reports an open-market purchase of common stock. The transaction code is “P,” which corresponds to a purchase in the open market or a private transaction, rather than a grant, option exercise, tax withholding, or other non-market event.

How do Fairmount and its managers describe their beneficial ownership of Zenas BioPharma (ZBIO) shares?

Fairmount, Peter Harwin, and Tomas Kiselak disclaim beneficial ownership of the reported securities except for their pecuniary interest. This means they report the holdings due to their roles but state that economic interest is limited to what they personally stand to gain.

Is the Zenas BioPharma (ZBIO) Form 4 transaction reported as direct or indirect ownership?

The 150,000-share purchase is reported as indirect ownership by Fairmount Healthcare Fund II L.P. The ownership code is “I,” and the nature of ownership explicitly identifies the fund as the holder, rather than the individual reporting persons directly.